Locking mechanism for fluid pressure operated devices



Nov. 20, 1956 D. H. ALLBRIGHT v I 2,

LOCKING MECHANISM FOR FLUID PRESSURE OPERATED EDEVICE Filed June 15; 1953 i} @5711!!! ZVIl/iwh United States Patent LOCKING MECHANISM FOR FLUID PRESSURE OPERATED DEVICES Dennis Howard Allbright, Foleshill, Coventry, England, assignor to Dunlop Rubber Company Limited, London County, England, a British company Application June 15, 1953, Serial No. 361,750

Claims priority, application Great Britain June 27, 1952 Claims. (Cl. 121-40) This invention relates to a mechanism for locking the relatively movable parts of a fluid pressure operated device and particularly suitable for locking a fluid pressure operated jack at the end of its stroke.

Locking mechanisms of this type are known. There are, for example, ball locks in which balls are moved inwardly or outwardly by the piston of the jack at the end of its stroke to register in a groove in the cylinder wall or a member solid therewith, and are held therein by a spring-loaded locking piston to lock the jack'in the terminal position. In other constructions a springy digitated sleeve is employed having latches at the end of each arm which engage in a recess and are locked in it by a spring-loaded locking piston. The sleeve may be secured to the piston and the recess provided adjacent the base of the cylinder, or alternatively the sleeve may be secured to the base of the cylinder and the recess provided on a member movable with the piston. These mechanisms are usually unlocked by pressurizing the cylinder to move the locking piston back against its spring and so release the balls or latches as the case may be.

My invention provides an alternative type of locking mechanism.

In my invention a locking mechanism for two members relatively movable by fluid pressure comprises a catch adapted to lock together the relatively movable members upon their assuming a predetermined relative position and being positively moved by a fluid pressure responsive catch actuating member into a lock engageable position upon the application of fluid pressure to the relatively movable members to cause movement towards the predetermined position, whereby the relatively movable members are locked together upon reaching the predetermined relative position, and the catch being moved by the catch actuating member into a lock releasing position upon the application of fluid pressure to the relatively movable member to cause movement away from the predetermined position.

Two relatively movable members may be a cylinder and a piston working in it and the catch actuating member a piston also working in the cylinder. The catch and the catch actuating piston are preferably together associated with either the piston or the cylinder and a catch engagement member may be associated with the other relatively movable member, the catch actuating piston being axially slidable relative to the member with which it is associated to operate the catch.

The catch may be pivoted to its associated member I and be arranged to move either inwardly or outwardly to lock the other member. The catch moves angularly under the control of the catch actuating piston into and out of a position in which it is engageable with the catch engagement member which preferably has a ramp portion over which the catch rides to be trapped behind the catch engagement members.

The catch actuating piston may be moved in each direction by fluid pressure but is preferably spring loaded in one direction to urge the catch towards a lock-engage- 2,771,060 Patented Nov. 20, 1956 able position and movable in the opposite direction by the fluid pressure applied to the main piston to move it into mechanism in the lock-releasing position.

Figure 2 is a sectional view on the line 2-2 in Figure 1.

Figure 3 is a sectional elevation similar to part of Figure 1 showing the locking mechanism in the locking position.

The jack shown in the drawings has as is usual a cylinder 4 and a piston 5 working in it. The piston is secured to a piston-rod 6 which passes out of the cylinder through the cylinder end 7 for connection by an attachment eye 8 to a mechanism to be operated. Both ends of the cylinder, on each side of the piston are provided with ports 9, 9 for the entry of fluid under pressure and its exhaust, for reciprocating the piston in its cylinder in the normal way.

The cylinder end 7 through which the piston-rod passes 11 has a fixed sleeve 10 extending axially into the cylinder which provides a bearing for the piston-rod 6. Sealing rings 11 prevent leakage of fluid from the cylinder along the piston-rod 6. An annular catch actuating piston 12 works in the annular space between the surface of the cylinder 4 and the sleeve 10 and is slidable in fluid-tight engagement with the sleeve 10 as well as the cylinder.

The annular catch actuating piston 12 is stepped, hav-.

ing an outer portion 13 having an external cylindrical surface on one side of a radial annular portion 14 and on the opposite side an inner cylindrical portion 15 slidable on the sleeve 10. Around the inner cylindrical portion 15 a helical compression spring 16 is fitted between the radial annular portion 14 and the cylinder end 7 to urge the catch actuating piston 12 forwards, that is away from the cylinder end 7. Rings 17 provide a fluid-tight.

seal between the sleeve and the bore ofthe inner portion 15 and rings 18 seal the joint between the outer portion 13 and the cylinder 4.

The forward part of the outer portion 13 tapers in a forward direction and is provided with equally spaced radial slots 19 in which catches 20 are guided. Each catch 20 has a part-cylindrical boss 21 by which it is pivotally mounted in a circumferential groove 30 of partcircular cross-section in the sleeve 10. The bore of the catch actuating piston 12 has an undercut recess 22 to the rear of the slots 19 and into which the slots open. The side of the recess 22 slopes outwardly from the forward part of the piston 12 towards the rear part. Into this recess 22 a rearwardly and slightly outwardly directed tail 23 on each catch 20 projects to be engaged by the sloping surface of the recess 22 on rearward movement of the catch actuating piston-12 to move the catch heads 26 outwardly. Immediately above the boss 21 each catch has a shoulder 24 with a rearward radial face which is engageable by a forward face 25 in the slot 19 and in the outer portion 13 of the catch actuating piston 12. On forward movement of the catch actuating piston 12 the face 25 engages the shoulder 24 to pivot the catch 20 and move the catch heads 26 inwardly.

Each catch 20 has a forwardly extending portion provided with an inwardly directed catch head 26. 'Within the hollow skirt of the piston 5 is a rearwardly directed axial spigot whose outer periphery is shaped to form a catch engagement member 27 having a radial annular forward face 28 and a frusto-conical rearward face 29.

When fluid under pressure is applied to the end of the cylinder 4 on the side of the piston away from the piston rod 6 the piston is moved rearwardly towards a position in which, the piston-rod. 6v is fully extended fromlhe. cylinder. piston is. held. in the,for,ward position; by the compression spring 16 and the catches 20.are held. as, shown in Figure 3, with their forwardly extending portions lying along the surface of the sleeve 10 andtheir catchf heads 26. in their innermost position. In this position the-lock is engageable and as the jack. piston approaches the extreme rear end of its travel. in which the. piston-rod 6 is. fully extended the catch heads 26. are engaged by the frusto-conical surface 29 which forms aramp to: deflect the catch heads 26. outwards against the loading. Of the spring 16 until, when the piston reaches the extreme position, the catch heads.2 6 drop inwards, urged by the spring 16, and are trapped by the forward face 28 of the catch. engagement member. The-catches 20! hold thepiston in the locking position until fluid, pressure is applied to the end of the cylinder 4 on the piston-rod side of the piston. The forward face. of the catch-actuating piston 12. is exposed to thispressure and is moved rearwardly by it against the spring 16. This moves the catches angnlarly to release the catch heads 26 from the catch engagement member 27 allowing the jack piston 5 to be moved forwards by the fluid pressure. The. catches 20.

are heldin the lock-releasing position until thefluid pressure in the cylinder on the piston-rod side of the piston is released.

The jack may alternatively or additionally be provided with a locking mechanism to lock the-piston at the oppo site end of its stroke. In such a case alocking mechanism, as described above, will be provided at the other end ofthe cylinder and the piston provided on the side opposite the piston-rod with a catch engagement member.

Having. now described my invention, what I claim is:

1. A locking mechanism for two members movable relative to each other which comprises one member having an annular recess coaxial with the line of movement of said members, and a second member having a circular flange coaxial with the line e f-movement of said members, separate, individual, locking elements arranged at intervals about the line of movement of said elements, each having a rocking engagement in said recess and Under these conditions the, catch. actuating;

having a lipped catch to engage the flange of said second member and having a shoulder and a tail portion, and a sliding member spring pressed in one direction to about said shoulder and movable in the opposite direction to engage said tail portion and to rock said locking element to disengage said lipped catch from said second element.

2. A locking mechanism for two members movable relatively to each other whichcomprisesa cylinder, a piston in said cylinder having a circular recess, an anchoring block fixedin saidcylinder and having anannular groove co-axial with said cylinder, a series of individual locking elements positioned about the axis of said cylinder, each having a projection intosaid groove to anchor said elements rockably therein and having a. lipped catch to engage said recess, a shoulder and an outwardly extending tail, and a sleeve spring pressed to engage the shoulders of said locking elements to rock their lipped catches into said recess. and? movable in the opposite directionto engage the tails. of said-locking elementsto rock them to disengage said lipped catches from said recess.

3. The locking m e h n n :0fiCIa,im;2 having guiding slots: in said anchoring block to guide said locking elements.

4. The locking mechanism of claim 2; in whichtsaid sleeve-is. moved against the spring; actionby fluid admit:

tedtosaid cylinder between the piston and. the sliding sleeve.

5.. The locking mechanism of claim 2 in which said piston has a stem passing through saidanchoring. block;

References Cited in the file of this patent UNITED STATES PATENTS Great Britain July 30. 19,46. 

